Obesity and type 2 diabetes are occurring at epidemic rates in the United States and worldwide. The global burden of diabetes is estimated to double over the next 25 years. Obese children are at risk for the development of insulin resistance, relative insulin deficiency and type 2 diabetes mellitus. The prevention of type 2 DM is hindered by the lack of a non-invasive predictive test, knowledge as to individual risk and effective preventative measures. There is increasing evidence that alterations in mitochondria contribute to the development of diabetes in humans. Therefore, it is important to explore mitochondrial dysfunction as a potential predictor of diabetes in children and a potential target for prevention. The aims of the proposed protocol are to determine whether an intensive exercise intervention can improve mitochondrial function in children identified as having mitochondrial dysfunction and insulin resistance. The use of a non-invasive imaging technique will allow for a functional in vivo assessment of mitochondrial activity. We propose the investigation of an intensive exercise protocol designed to improve mitochondrial function in children who are insulin resistant and have documented mitochodrial dysfunction by magnetic resonance spectroscopy. The study is designed to investigate the plasticity of abnormal mitochondrial function in high risk children. In summary, the proposed projects will investigate mitochondrial function as a non-invasive predictive marker for the development of insulin resistance and type 2 diabetes mellitus in children and attempt to modify mitochondrial function with an intensive exercise intervention. The study of mitochondrial dysfunction in children may both identify those at risk for disease and provide a molecular therapeutic target for prevention and treatment.